Channel scanning method and apparatus

ABSTRACT

A receiver is tuned to a first channel in a plurality of channels, and at least one beacon signal from at least one other channel is received while the receiver is tuned to the first channel. The at least one other channel is determined to be active based on the at least one beacon signal received while the receiver is tuned to the first channel. A channel that is determined to be “active” may be, for example, a communication channel on which an access point in a communication network is communicating or is able to communicate.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims the benefit of U.S. ProvisionalApplication No. 60/863,676, entitled “WIDEBAND SCANNING,” filed on Oct.31, 2006, which is hereby incorporated by reference herein in itsentirety.

FIELD OF TECHNOLOGY

The present disclosure relates generally to communication systems, andmore particularly, to wireless communication systems that utilizemultiple communication channels.

DESCRIPTION OF THE RELATED ART

An ever-increasing number of relatively cheap, low power wireless datacommunication services, networks and devices have been made availableover the past number of years, promising near wire speed transmissionand reliability. Various wireless technologies are described in detailin the 802.11 IEEE Standard, including for example, the IEEE Standard802.11 (1999) and its updates and amendments, the IEEE Standard802.11a/g (2003), as well as the IEEE Standard 802.11n now in theprocess of being adopted, all of which are collectively incorporatedherein fully by reference. These standards have been or are in theprocess of being commercialized with the promise of 54 Mbps or moreeffective bandwidth, making them a strong competitor to traditionalwired Ethernet and the more ubiquitous “802.11b” or “WiFi” 11 Mbpsmobile wireless transmission standard.

Generally speaking, transmission systems compliant with the IEEE 802.11aand 802.11g or “802.11a/g” as well as the 802.11n standards achievetheir high data transmission rates using Orthogonal Frequency DivisionModulation or OFDM encoded symbols mapped up to a 64 quadratureamplitude modulation (QAM) multi-carrier constellation. In a generalsense, the use of OFDM divides the overall system bandwidth into anumber of frequency sub-bands or channels, with each frequency sub-bandbeing associated with a respective sub-carrier upon which data may bemodulated. Thus, each frequency sub-band of the OFDM system may beviewed as an independent transmission channel within which to send data,thereby increasing the overall throughput or transmission rate of thecommunication system.

Transmitters used in the wireless communication systems that arecompliant with the aforementioned 802.11a/802.11g/802.11n standards aswell as other standards such as the 802.16a/d/e/m IEEE Standards,typically perform multi-carrier OFDM symbol encoding (which may includeerror correction encoding and interleaving), convert the encoded symbolsinto the time domain using Inverse Fast Fourier Transform (IFFT)techniques, and perform digital to analog conversion and conventionalradio frequency (RF) upconversion on the signals. These transmittersthen transmit the modulated and upconverted signals after appropriatepower amplification to one or more receivers, resulting in a relativelyhigh-speed time domain signal with a large peak-to-average ratio (PAR).

Likewise, the receivers used in the wireless communication systems thatare compliant with the aforementioned 802.11a/802.11g/802.11n and802.16a IEEE standards typically include an RF receiving unit thatperforms RF downconversion and filtering of the received signals (whichmay be performed in one or more stages), and a baseband processor unitthat processes the OFDM encoded symbols bearing the data of interest.The digital form of each OFDM symbol presented in the frequency domainis recovered after baseband downconverting, conventional analog todigital conversion and Fast Fourier Transformation of the received timedomain analog signal. Thereafter, the baseband processor performsdemodulation (phase rotation) and frequency domain equalization (FEQ) torecover the transmitted symbols, and these symbols are then processed ina Viterbi decoder to estimate or determine the most likely identity ofthe transmitted symbol. The recovered and recognized stream of symbolsis then decoded, which may include deinterleaving and error correctionusing any of a number of known error correction techniques, to produce aset of recovered signals corresponding to the original signalstransmitted by the transmitter.

In the aforementioned 802.11a/802.11g/802.11n and 802.16a IEEEstandards, a radio frequency spectrum is partitioned into a plurality ofchannels so that different information signals may be transmitted on thedifferent channels. In such systems, an information signal is shifted toits RF channel for transmission. Each RF channel may be defined by itscenter frequency and its bandwidth or its upper and lower frequencies,for example. In some systems, each channel may be assigned a number orsome other identifier so that the channels may be referred to moreeasily.

When a communication device for use in such a system powers up in analready existing wireless network, it may attempt to find a wirelessaccess point and determine on which channel it may communicate with theaccess point. To facilitate the discovery of access points, an accesspoint periodically may transmit a signal often referred to as a beaconto let other communication devices know of its presence. The beacon willinclude various information including a channel number to indicate whichchannel it is using.

When a communication device seeks to establish a connection with anaccess point, it may scan each channel in the wireless network systemfor beacons. Scanning for beacons includes tuning to each of thechannels of the system and listening for beacons for some period of timeat each channel. For example, if there are fourteen channels and it isassumed that beacons are transmitted at 100 millisecond (ms) intervals,the communication device may listen for beacons for approximately 100 msat each channel. Thus, the communication device may spend 1.4 seconds(100 ms/channel×14 channels) scanning for beacons.

SUMMARY OF THE DISCLOSURE

In one embodiment, a method comprises tuning a receiver to a firstchannel in a plurality of channels, and receiving at least one beaconsignal from at least one other channel while the receiver is tuned tothe first channel. The method also comprises determining that the atleast one other channel is active based on the at least one beaconsignal received while the receiver is tuned to the first channel. Achannel that is “active,” as the term is used herein, may refer to acommunication channel on which an access point in a communicationnetwork is communicating or is able to communicate. More broadly,channel that is “active,” as the term is used herein, may refer to acommunication channel on which beacons are being transmitted.

In another embodiment, a method comprises tuning a receiver to a firstchannel, the first channel in a first subset of channels, and scanningthe first subset of channels for one or more beacon signals while thereceiver is tuned to the first channel. The method additionallycomprises tuning the receiver to a second channel, the second channel ina second subset of channels different than the first subset of channels,and scanning the second subset of channels for one or more beaconsignals while the receiver is tuned to the second channel.

In yet another embodiment, in which a multi-channel communication systemhas N communication channels, wherein N is a positive integer greaterthan two, a method for searching for active channels, comprises tuning areceiver to each of M communication channels, wherein M is less than N.The method also comprises scanning all N communication channels for oneor more beacon signals without tuning the receiver to all Ncommunication channels.

In still another embodiment, a communication device comprises a radiofrequency (RF) receiver having a filter. The device also comprises acontroller coupled to the RF receiver. The controller causes thereceiver to be tuned to a first channel in a plurality of channels,detects at least one beacon signal from at least one other channel whilethe receiver is tuned to the first channel, the at least one otherchannel falling at least partially within a passband of the filter, anddetermines that the at least one other channel is active based on the atleast one beacon signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram an example receiver for use in an OFDM-basedcommunications system;

FIG. 2 is a frequency-domain diagram illustrating the locations ofchannels in a wireless communication network that conforms to the IEEE802.11 standard;

FIG. 3 is a flow diagram of an example method for scanning channels forbeacons;

FIG. 4 is a flow diagram of a specific embodiment of the method of FIG.3;

FIG. 5A is a block diagram of a high definition television that mayutilize channel scanning techniques such as described herein;

FIG. 5B is a block diagram of a vehicle that may utilize channelscanning techniques such as described herein;

FIG. 5C is a block diagram of a cellular phone that may utilize channelscanning techniques such as described herein;

FIG. 5D is a block diagram of a set top box that may utilize channelscanning techniques such as described herein;

FIG. 5E is a block diagram of a media player that may utilize channelscanning techniques such as described herein; and

FIG. 5F is a block diagram of a voice over IP device that may utilizechannel scanning techniques such as described herein.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of an example OFDM receiver 100. The receiver100 includes a radio frequency (RF) downconverter 104 that receives anOFDM signal that has been modulated to an RF channel and shifts the OFDMsignal from the RF channel to baseband. The RF downconverter 104 may beany of a variety of types of RF downconverters including, for example, adirect conversion downconverter, a super heterodyne downconverter, etc.

A filter 106 is coupled to the RF downconverter 104 and filters anoutput of the RF downconverter 104. Depending on the particularimplementation, the filter 106 may be a fixed filter or a tunablefilter. In implementations using a super heterodyne downconverter, thefilter 106 optionally may operate on an intermediate frequency (IF) asopposed to operating at baseband. The filter 106 may have a 20 MHzpassband, for example, if the receiver 100 is to be compatible with theIEEE 802.11 standard. The filter 106 alternatively may have a 40 MHzpassband if the receiver 100 is to support channel bonding, for example.Of course, the filter 106 may have a bandwidth that is different than 20MHz or 40 MHz depending upon the particular implementation of thereceiver 100.

An analog-to-digital converter (ADC) 108 coupled to the RF downconverter104 (via the filter 106) samples the downconverted signal. An output(y(n)) of the ADC 108 includes signal information corresponding to OFDMsymbols and signal information corresponding to guard intervals, whichmay include a cyclic prefix, for example. A cyclic prefix is merely acopy of an ending portion of the OFDM symbol inserted in the guardinterval that precedes the OFDM symbol.

A windowing block 112 is coupled to the ADC 108 The windowing block 108provides a block of signal samples x₀, x₁, x_(N-1) to a fast Fouriertransform calculation block 116 (such as a Fourier transform (FFT)block) to which the windowing block 112 is coupled. The signal samplesx₀, x₁, x_(N-1) correspond to an OFDM symbol. In other words, thewindowing block 112 attempts to extract OFDM symbols from the signaly(n). The FFT block 116 performs an FFT operation on the set of N signalsamples x₀, x₁, x_(N-1) and generates a set of N signals X₀, X₁, . . .X_(N-1) that correspond to the OFDM symbol. Each of the N signals X₀,X₁, . . . X_(N-1) may be a quadrature amplitude modulation (QAM),phase-shift keying (PSK), etc., modulated signal. A symboldetector/de-multiplexer 120 is coupled to the FFT block 116 and mapseach of the signals X₀, X₁, . . . X_(N-1) to a set of one or more bits,depending on the particular modulation scheme that is employed.Additionally, the symbol detector/de-multiplexer 120 demultiplexes theparallel sets of bits to form a serial information signal s(i). Thesymbol detector/de-multiplexer 120 may include a Viterbi decoder. Anerror corrector 124 operates on the information signal s(i) and attemptsto correct errors in the signal s(i).

Additionally, the receiver 100 includes a controller 132 coupled to theRF demodulator 104. The controller 132 generates a control signal thatcauses the RF demodulator 104 to tune to a particular RF channel.Further, the receiver 100 includes a beacon detector 136 coupled to thecontroller 132. The beacon detector 136 analyzes the information signals(i) to detect beacons. When a beacon is detected, the beacon detector136 may forward the beacon and/or information included in the beacon tothe controller 132. Although in FIG. 1 the beacon detector 136 isillustrated as being separate from the controller 132, in someimplementations the beacon detector may be implemented by the controller132.

FIG. 2 is a frequency-domain diagram illustrating the locations ofchannels 200 in a wireless communication network that conforms to theIEEE 802.11 standard. In the network corresponding to FIG. 2, there areeleven channels 200 available, and each channel 200 overlaps withadjacent channels. For example, channels 1-11 have center frequencieslocated approximately every 5 MHz starting at 2.412 GHz, and eachchannel is approximately 20 MHz wide. FIG. 2 also illustrates thefrequency responses 204 of the filter 106 when the passband isapproximately 20 MHz wide and when it is approximately 40 MHz wide. InFIG. 2, the passband of the filter 106 is centered at approximately2.437 GHz which corresponds to the receiver 100 being tuned to Channel6.

As can be seen in FIG. 2; significant portions of other channels fallwithin the passband of the filter 106 when the receiver 100 is tuned toChannel 6. For example, with the 20 MHz bandwidth filter 106,significant portions of Channels 5 and 7 fall within its passband.Similarly, with the 40 MHz bandwidth filter 106, significant portions ofChannels 3, 4, 5, 7, 8 and 9 fall within its passband. As a result, thereceiver 100 is often able to decode beacons sent on adjacent channels.Thus, the receiver 100 can scan for beacons on multiple channels whileit is tuned to a single channel. Beacon signals include informationindicating the channel on which it was transmitted. Therefore, thereceiver 100 can analyze a beacon signal to determine via which channelthe beacon was received.

FIG. 3 is a flow diagram of an example method 250 for scanning channelsfor beacons that may be implemented by a receiver such as the examplereceiver 100 of FIG. 1. For ease of explanation, the method 250 will bedescribed with reference to FIGS. 1 and 2. Of course, the method 250 maybe implemented by a receiver different than the receiver 100 and in acommunication network having a different set of channels as compared tothe channels in FIG. 2.

At a block 254, the receiver may be tuned to a channel. For example, thecontroller 132 may cause the RF downconverter 104 to be tuned to aparticular channel. Then, at a block 258, a subset of channels isscanned for beacons while the receiver remains tuned to a singlechannel. Scanning for beacons may include detecting beacons and storingin a memory indications of channels on which beacons were detected. Forexample, the beacon signal may include data that indicates that channelon which it was transmitted. Detecting beacons may be performed by thebeacon detector 136, for example. Storing indications of channels onwhich beacons were detected may be performed by the controller 132. Theindications may be stored in a memory of or coupled to the controller132, for example.

Referring to FIG. 2, for example, if the receiver is tuned to Channel 6and if the 20 MHz filter is being used, the subset of Channels 5-7 maybe scanned. If the 40 MHz filter is being used, the subsets of Channels3-9, Channels 4-8, or Channels 5-7 may be scanned, depending on theparticular implementation. Scanning at the block 258 may be performedfor some period greater than the interval period at which access pointstransmit beacons in the communication system. For example, scanning atthe block 258 may be performed for a period that is between one and twobeacon interval periods. As further alternative examples, scanning atthe block 258 may be performed for a period that is between 1 and 1.25beacon interval periods, 1.1 and 1.5 beacon interval periods, 1.5 andtwo beacon interval periods, etc. The particular period for whichscanning at the block 258 may be performed may depend on the particularimplementation.

At a block 262, it may be determined if there are more channels to scan.For example, determining if there are more channels may includeanalyzing an order or list of channels. As another example, determiningif there are more channels may include adding an offset to a currentchannel number and determining if the sum is greater than a lastchannel. If there are no more channels to scan, the flow may end.Otherwise, the flow proceeds to a block 266, at which the receiver istuned to a different channel. Determination of the different channel towhich to tune the receiver may be determined in a variety of ways. Forexample, determining the different channel may include analyzing anorder or list of channels. Also, determining the different channel maybe based on a variety of factors. For example, it may be based on whichchannels have already been scanned. It also may be based on the channelto which the receiver is currently tuned. It also may be based on thebandwidth of the filter 106. Further, it may be based on a fixedsequence of channels or a fixed step size (e.g., next channel=currentchannel+step size). Next, the flow proceeds back to the block 258.

To further illustrate the method 250, specific examples will bediscussed with respect to FIG. 2. These examples are set forth as tablesin which the ordering of the rows corresponds to the sequence ofchannels to which the receiver tunes while the method 250 isimplemented. For example, in Table 1, the receiver is first tuned toChannel 1, then to Channel 4, then to Channel 7, and finally to Channel11. The second columns of the tables indicate the channels that arescanned while the receiver is tuned to a particular example. In Table 1,for example, Channels 3, 4, and 5 are scanned while the receiver istuned to Channel 4.

Tables 1 and 2 are examples in which the receiver utilizes a filter 106having a 20 MHz passband.

TABLE 1 Channel to Which Receiver Channels is Tuned Scanned 1 1, 2 4 3,4, 5 7 6, 7, 8 10 9, 10, 11

TABLE 2 Channel to Which Receiver Channels is Tuned Scanned 2 1, 2, 3 54, 5, 6 8 7, 8, 9 11 10, 11

Tables 3-9 are examples in which the receiver utilizes a filter 106having a 40 MHz passband.

TABLE 3 Channel to Which Receiver Channels is Tuned Scanned 1 1, 2, 3, 44 1, 2, 3, 4, 5, 6, 7 7 4, 5, 6, 7, 8, 9, 10 10 7, 8, 9, 10, 11

TABLE 4 Channel to Which Receiver Channels is Tuned Scanned 2 1, 2, 3,4, 5 5 2, 3, 4, 5, 6, 7, 8 8 5, 6, 7, 8, 9, 10, 11 11 8, 9, 10, 11

TABLE 5 Channel to Which Receiver Channels is Tuned Scanned 3 1, 2, 3,4, 5, 6 6 3, 4, 5, 6, 7, 8, 9 9 6, 7, 8, 9, 10, 11 11 7, 8, 9, 10, 11

TABLE 6 Channel to Which Receiver Channels is Tuned Scanned 1 1, 2, 3, 46 3, 4, 5, 6, 7, 8, 9 11 8, 9, 10, 11

TABLE 7 Channel to Which Receiver Channels is Tuned Scanned 3 1, 2, 3,4, 5, 6 8 5, 6, 7, 8, 9, 10, 11 11 8, 9, 10, 11

TABLE 8 Channel to Which Receiver Channels is Tuned Scanned 3 1, 2, 3,4, 5, 6 9 6, 7, 8, 9, 10, 11

TABLE 9 Channel to Which Receiver Channels is Tuned Scanned 3 1, 2, 3,4, 5, 6 8 5, 6, 7, 8, 9, 10, 11

As can be seen in the examples corresponding to Tables 1-9, if a filterwith a 40 MHz passband is utilized, it may take less loops through themethod 250 as compared to utilizing a filter with a 20 MHz passbandbecause more Channels potentially can be scanned while the receiver istuned to a single Channel.

Of course, in examples corresponding to Tables 1-9, the receiver neednot be tuned in forward order (i.e., from the first row to the lastrow). Rather, the receiver could be tuned in reverse order (i.e., fromthe last row to the first row) or some other order. Referring to Table1, as just one example, the receiver could first be tuned to Channel 4,then to Channel 1, then to Channel 11, and finally to Channel 7.

FIG. 4 is a flow diagram of an example method 300 for scanning channelsfor beacons that may be implemented by a receiver such as the examplereceiver 100 of FIG. 1. The method 300 is another embodiment of themethod 250 of FIG. 3. For ease of explanation, the method 300 will bedescribed with reference to FIGS. 1 and 2. Of course, the method 300 maybe implemented by a receiver different than the receiver 100 and in acommunication network having a different channel configuration ascompared to the channels in FIG. 2.

At a block 304, a receiver may be tuned to a first channel in an orderof channels. For example, the controller 132 may cause the RFdownconverter 104 to tune the receiver 100 to a first channel in theorder. An indication of the order may be stored in a memory that is acomponent of or coupled to the controller 132. Referring to FIG. 2, theorder may be an ordering of the Channels 1-11. For example, the ordercould be Channel 1, Channel 2, . . . , Channel 11. Of course, differentorderings could be utilized as well.

At a block 308, as subset of channels may be scanned while the receiveris tuned to the single channel. The block 308 may be implemented similarto the block 258 of FIG. 3, for example. At a block 312, indications ofchannels on which beacons were detected, if any, may be stored. Forexample, the controller 132 may store indications of the channels onwhich beacons were detected in a memory that is part of or coupled tothe controller 132.

At a block 316, it may be determined if there are any channels in theorder to which the receiver was not already tuned and for which a beaconhas not yet been detected. If there are no such channels, the flow mayend. If there are one or more such channels, the flow may proceed to ablock 320.

At the block 320, the next channel in the order to which the receiverwas not already tuned and for which a beacon has not yet been detectedis determined and the receiver is tuned to that channel. Then, the flowreturns to the block 308.

Although the methods of FIGS. 2 and 3 were described with reference toan OFDM-based system, it is to be understood that the channel scanningtechniques may be used in systems that use modulation techniques otherthan OFDM.

Referring now to FIGS. 5A-5F, various example devices will be describedthat may utilize channel scanning techniques such as described above.Referring to FIG. 5A, such techniques may be utilized in a highdefinition television (HDTV) 620. The HDTV 620 includes signalprocessing and/or control circuits, which are generally identified inFIG. 5A at 622, a WLAN interface 629, and a mass data storage 627.Channel scanning techniques may be utilized in the WLAN interface 629 orthe signal processing circuit and/or control circuit 622, for example.HDTV 620 receives HDTV input signals in either a wired or wirelessformat and generates HDTV output signals for a display 626. In someimplementations, signal processing circuit and/or control circuit 622and/or other circuits (not shown) of HDTV 620 may process data, performcoding and/or encryption, perform calculations, format data and/orperform any other type of HDTV processing that may be required.

HDTV 620 may communicate with mass data storage 627 that stores data ina nonvolatile manner such as optical and/or magnetic storage devices.The mass data storage 627 may include one or more hard disk drives(HDDs) and/or one or more digital versatile disks (DVDs). One or more ofthe HDDs may be a mini HDD that includes one or more platters having adiameter that is smaller than approximately 1.8″. HDTV 620 may beconnected to memory 628 such as RAM, ROM, low latency nonvolatile memorysuch as flash memory and/or other suitable electronic data storage. HDTV620 also may support connections with a WLAN via the WLAN networkinterface 629.

Referring now to FIG. 5B, techniques such as described above may beutilized in a control system of a vehicle 630. In some implementations,a powertrain control system 632 receives inputs from one or more sensorssuch as temperature sensors, pressure sensors, rotational sensors,airflow sensors and/or any other suitable sensors and/or that generatesone or more output control signals such as engine operating parameters,transmission operating parameters, and/or other control signals.

A control system 640 may likewise receive signals from input sensors 642and/or output control signals to one or more output devices 644. In someimplementations, control system 640 may be part of an anti-lock brakingsystem (ABS), a navigation system, a telematics system, a vehicletelematics system, a lane departure system, an adaptive cruise controlsystem, a vehicle entertainment system such as a stereo, DVD, compactdisc and the like. Still other implementations are contemplated.

Powertrain control system 632 may communicate with mass data storage 646that stores data in a nonvolatile manner. Mass data storage 646 mayinclude optical and/or magnetic storage devices for example hard diskdrives HDD and/or DVDs. One or more of the HDDs may be a mini HDD thatincludes one or more platters having a diameter that is smaller thanapproximately 1.8″. Powertrain control system 632 may be connected tomemory 647 such as RAM, ROM, low latency nonvolatile memory such asflash memory and/or other suitable electronic data storage. Powertraincontrol system 632 also may support connections with a WLAN via a WLANnetwork interface 648. Channel scanning techniques such as describedabove may be implemented in the WLAN interface 648. The control system640 may also include mass data storage, memory and/or a WLAN interface(all not shown).

Referring now to FIG. 5C, techniques such as described above may also beutilized in a cellular phone 650 that may include a cellular antenna651. The cellular phone 650 includes signal processing and/or controlcircuits, which are generally identified in FIG. 5C at 652, a WLANinterface 668, and a mass data storage 664. Channel scanning techniquesmay be implemented in the signal processing and/or control circuits 652and/or the WLAN interface 668, for example. In some implementations,cellular phone 650 includes a microphone 656, an audio output 658 suchas a speaker and/or audio output jack, a display 660 and/or an inputdevice 662 such as a keypad, pointing device, voice actuation and/orother input device. Signal processing and/or control circuits 652 and/orother circuits (not shown) in cellular phone 650 may process data,perform coding and/or encryption, perform calculations, format dataand/or perform other cellular phone functions.

Cellular phone 650 may communicate with mass data storage 664 thatstores data in a nonvolatile manner such as optical and/or magneticstorage devices for example hard disk drives HDD and/or DVDs. At leastone HDD may be a mini HDD that includes one or more platters having adiameter that is smaller than approximately 1.8″. Cellular phone 650 maybe connected to memory 666 such as RAM, ROM, low latency nonvolatilememory such as flash memory and/or other suitable electronic datastorage. Cellular phone 650 also may support connections with a WLAN viaa WLAN network interface 668.

Referring now to FIG. 5D, techniques such as described above may beutilized in a set top box 680. The set top box 680 includes signalprocessing and/or control circuits, which are generally identified inFIG. 5D at 684, a WLAN interface 696, and a mass data storage device690. Channel scanning techniques may be implemented in the signalprocessing and/or control circuits 684 and/or the WLAN interface 696,for example. Set top box 680 receives signals from a source such as abroadband source and outputs standard and/or high definition audio/videosignals suitable for a display 688 such as a television and/or monitorand/or other video and/or audio output devices. Signal processing and/orcontrol circuits 684 and/or other circuits (not shown) of the set topbox 680 may process data, perform coding and/or encryption, performcalculations, format data and/or perform any other set top box function.

Set top box 680 may communicate with mass data storage 690 that storesdata in a nonvolatile manner. Mass data storage 690 may include opticaland/or magnetic storage devices for example hard disk drives HDD and/orDVDs. At least one HDD may be a mini HDD that includes one or moreplatters having a diameter that is smaller than approximately 1.8″. Settop box 680 may be connected to memory 694 such as RAM, ROM, low latencynonvolatile memory such as flash memory and/or other suitable electronicdata storage. Set top box 680 also may support connections with a WLANvia the WLAN network interface 696.

Referring now to FIG. 5E, techniques such as described above may beutilized in a media player 700. The media player 700 may include signalprocessing and/or control circuits, which are generally identified inFIG. 5E at 704, a WLAN interface 716, and a mass data storage device710. Channel scanning techniques may be implemented in the signalprocessing and/or control circuits 704 and/or the WLAN interface 716,for example. In some implementations, media player 700 includes adisplay 707 and/or a user input 708 such as a keypad, touchpad and thelike. In some implementations, media player 700 may employ a graphicaluser interface (GUI) that typically employs menus, drop down menus,icons and/or a point-and-click interface via display 707 and/or userinput 708. Media player 700 further includes an audio output 709 such asa speaker and/or audio output jack. Signal processing and/or controlcircuits 704 and/or other circuits (not shown) of media player 700 mayprocess data, perform coding and/or encryption, perform calculations,format data and/or perform any other media player function.

Media player 700 may communicate with mass data storage 710 that storesdata such as compressed audio and/or video content in a nonvolatilemanner. In some implementations, the compressed audio files includefiles that are compliant with MP3 format or other suitable compressedaudio and/or video formats. The mass data storage may include opticaland/or magnetic storage devices for example hard disk drives HDD and/orDVDs. At least one HDD may be a mini HDD that includes one or moreplatters having a diameter that is smaller than approximately 1.8″.Media player 700 may be connected to memory 714 such as RAM, ROM, lowlatency nonvolatile memory such as flash memory and/or other suitableelectronic data storage. Media player 700 also may support connectionswith a WLAN via a WLAN network interface 716. Still otherimplementations in addition to those described above are contemplated.

Referring to FIG. 5F, techniques such as described above may be utilizedin a Voice over Internet Protocol (VoIP) phone 750 that may include anantenna 754, signal processing and/or control circuits 758, a wirelessinterface 762, and a mass data storage 766. Channel scanning techniquesdescribed above may be implemented in the signal processing and/orcontrol circuits 758 and/or the wireless interface 762, for example. Insome implementations, VoIP phone 750 includes, in part, a microphone770, an audio output 774 such as a speaker and/or audio output jack, adisplay monitor 778, an input device 782 such as a keypad, pointingdevice, voice actuation and/or other input devices, and a WirelessFidelity (Wi-Fi) communication module 762. Signal processing and/orcontrol circuits 758 and/or other circuits (not shown) in VoIP phone 750may process data, perform coding and/or encryption, performcalculations, format data and/or perform other VoIP phone functions.

VoIP phone 750 may communicate with mass data storage 766 that storesdata in a nonvolatile manner such as optical and/or magnetic storagedevices, for example hard disk drives HDD and/or DVDs. The HDD may be amini HDD that includes one or more platters having a diameter that issmaller than approximately 1.8″. VoIP phone 750 may be connected tomemory 786, which may be a RAM, ROM, low latency nonvolatile memory suchas flash memory and/or other suitable electronic data storage. VoIPphone 750 is configured to establish communications link with a VoIPnetwork (not shown) via Wi-Fi communication module 762.

The various blocks, operations, and techniques described above may beimplemented in hardware, firmware, software, or any combination ofhardware, firmware, and/or software. When implemented in software, thesoftware may be stored in any computer readable memory such as on amagnetic disk, an optical disk, or other storage medium, in a RAM or ROMor flash memory of a computer, processor, hard disk drive, optical diskdrive, tape drive, etc. Likewise, the software may be delivered to auser or a system via any known or desired delivery method including, forexample, on a computer readable disk or other transportable computerstorage mechanism or via communication media. Communication mediatypically embodies computer readable instructions, data structures,program modules or other data in a modulated data signal such as acarrier wave or other transport mechanism. The term “modulated datasignal” means a signal that has one or more of its characteristics setor changed in such a manner as to encode information in the signal. Byway of example, and not limitation, communication media includes wiredmedia such as a wired network or direct-wired connection, and wirelessmedia such as acoustic, radio frequency, infrared and other wirelessmedia. Thus, the software may be delivered to a user or a system via acommunication channel such as a telephone line, a DSL line, a cabletelevision line, a wireless communication channel, the Internet, etc.(which are viewed as being the same as or interchangeable with providingsuch software via a transportable storage medium). When implemented inhardware, the hardware may comprise one or more of discrete components,an integrated circuit, an application-specific integrated circuit(ASIC), etc.

While the present invention has been described with reference tospecific examples, which are intended to be illustrative only and not tobe limiting of the invention, it will be apparent to those of ordinaryskill in the art that changes, additions or deletions in addition tothose explicitly described above may be made to the disclosedembodiments without departing from the spirit and scope of theinvention.

What is claimed is:
 1. A method, comprising: tuning a wireless localarea network (WLAN) receiver to a first channel of a plurality ofchannels; receiving at least one WLAN beacon signal from at least oneother channel of the plurality of channels while the WLAN receiver istuned to the first channel, including decoding the at least one WLANbeacon signal received while the WLAN receiver is tuned to the firstchannel; and while the WLAN receiver is tuned to the first channel,determining the identity of the at least one other channel by analyzinginformation in the decoded WLAN beacon signal.
 2. A method according toclaim 1, wherein the plurality of channels includes N channels, whereinN is an integer greater than three; wherein the method further comprisesscanning all N channels by tuning the receiver to M channels, wherein Mis an integer less than N.
 3. A method according to claim 1, wherein thereceiver includes a filter with a passband having a 20 MHz bandwidth;wherein receiving at least one beacon signal from at least one otherchannel comprises receiving at least one beacon signal from at least oneother channel in a subset of at least two channels, the subset includingthe first channel.
 4. A method according to claim 3, wherein the subsetincludes three channels.
 5. A method according to claim 1, wherein thereceiver includes a filter with a passband having a 40 MHz bandwidth;wherein receiving at least one beacon signal from at least one otherchannel comprises receiving at least one beacon signal from at least oneother channel in a subset of at least five channels, the subsetincluding the first channel.
 6. A method according to claim 5, whereinthe subset includes seven channels.
 7. A method according to claim 5,wherein receiving at least one beacon signal comprises receiving abeacon signal modulated using OFDM.
 8. A method according to claim 1,further comprising determining that the at least one other channel isactive, including determining that an access point in a communicationnetwork is able to communicate via the at least one other channel.
 9. Amethod, comprising: tuning a wireless local area network (WLAN) receiverto a first channel, the first channel in a first subset of channels;scanning the first subset of channels for one or more WLAN beaconsignals while the WLAN receiver is tuned to the first channel,including, when a WLAN beacon signal from a channel adjacent to thefirst channel is received while the WLAN receiver is tuned to the firstchannel, decoding the WLAN beacon signal from the channel adjacent thefirst channel; tuning the WLAN receiver to a second channel, the secondchannel in a second subset of channels different than the first subsetof channels; scanning the second subset of channels for one or more WLANbeacon signals while the WLAN receiver is tuned to the second channel;decoding the one or more WLAN beacon signals to determine via which oneof the scanned second subset of channels the one or more WLAN beaconsignals are received while the WLAN receiver is tuned to the secondchannel, including, when a WLAN beacon signal from a channel adjacent tothe second channel is received while the WLAN receiver is tuned to thesecond channel, i) decoding the WLAN beacon signal from the channeladjacent the second channel and ii) determining the identity of thechannel adjacent to the second channel by analyzing information in thedecoded WLAN beacon signal.
 10. A method according to claim 9, whereinthe first subset of channels and the second subset of channels includeone or more of the same channels.
 11. A method according to claim 9,wherein the first subset of channels and the second subset of channelsdo not include any of the same channels.
 12. A method according to claim9, wherein multi-channel communication system includes N channels,wherein N is an integer greater than three; wherein the method furthercomprises scanning all N channels by tuning the receiver to M channels,wherein M is an integer less than N.
 13. A method according to claim 9,wherein the receiver includes a filter with a passband having a 20 MHzbandwidth; wherein the first subset includes at least two channels; andwherein the second subset includes at least two channels.
 14. A methodaccording to claim 13, wherein the first subset includes three channelsand the second subset includes three channels.
 15. A method according toclaim 9, wherein the receiver includes a filter with a passband having a40 MHz bandwidth; wherein the first subset includes at least fivechannels; and wherein the second subset includes at least five channels.16. A method according to claim 15, wherein the first subset includesseven channels and the second subset includes seven channels.
 17. Amethod according to claim 9, wherein scanning the first subset ofchannels includes receiving a beacon signal modulated using OFDM; andwherein scanning the second subset of channels includes receiving abeacon signal modulated using OFDM.
 18. In a multi-channel communicationsystem having N communication channels, wherein N is a positive integergreater than two, a method for searching for active channels, the methodcomprising: tuning a WLAN receiver to each of M communication channels,wherein M is a positive integer less than N; scanning-all Ncommunication channels for one or more WLAN beacon signals withouttuning the WLAN receiver to all N communication channels, including,when the WLAN receiver is tuned to a first channel and a WLAN beaconsignal from a second channel is received, decoding the WLAN beaconsignal from the second channel while the WLAN receiver is tuned to thefirst channel; and while the WLAN receiver is tuned to the firstchannel, analyzing information in the decoded WLAN beacon signal todetermine the identity of the second channel.
 19. A communicationdevice, comprising: a radio frequency (RF) WLAN receiver having afilter; a controller coupled to the RF WLAN receiver, the controller tocause the WLAN receiver to be tuned to a first channel in a plurality ofchannels, detect at least one WLAN beacon signal from at least one otherchannel while the WLAN receiver is tuned to the first channel, the atleast one other channel falling partially within a passband of thefilter, and determine the identity of the at least one other channelfalling partially within the passband of the filter based on decodingthe at least one WLAN beacon signal while the WLAN receiver is tuned tothe first channel, wherein determining the identity of the at least oneother channel includes analyzing information in the decoded WLAN beaconsignal.
 20. A communication device according to claim 19, wherein thecontroller is configured to determine that an access point in acommunication network is able to communicate via the at least one otherchannel.